1. Field of the Invention
This invention relates to circuit board ejector/injector systems and more particularly to those systems for use with a printed circuit board plug-in unit having an integral front panel, with a desired unit being insertable and removable from a card cage and with an injector/ejector mounted on the circuit board to facilitate the insertion and removal of the unit from the card cage.
2. The Prior Art
In the electronics industry, electronic components are often interconnected for mass manufacturing purposes by mounting them on printed circuit boards. The printed circuit boards are connected to other electrical devices by means of electrical connectors carried by the printed circuit boards. Groups of printed circuit boards are often interconnected by placing them in circuit board subracks, also known as card cages, that include mounting hardware for the printed circuit boards. The card cages include a pair of spaced card guides for slidably receiving the opposite edges of a printed circuit board. The card cages are interconnected with the printed circuit board by means of an electrical connector aligned with the electrical connector or connectors carried by the printed circuit board and to be placed in an electrically conductive circuit relationship therewith. In this arrangement, it is common for the end of the printed circuit board opposite to the end mounting the electrical connector to be secured in a perpendicular, integrated relationship with the panel member. This integral unit is referred to as a plug-in unit or plug-in module in the art.
The gripping action provided by the two interconnected electrical connectors: namely, the connector or connectors carried by the printed circuit board and the electrical connector associated with the subrack or card cage, make it difficult to remove the printed circuit board plug-in unit from the electrical connector of the card cage system. Typically, two handles are mounted on the front panel of the plug-in unit to permit the plug-in unit to be manually pulled from the card cage connectors. However, this is often not an easy task. Accordingly, ejectors have also been mounted on the front panel of some types of plug-in unit boards as an aid in extracting the printed circuit board plug-in unit from the electrical connector of the card cage or subrack. In this subrack or card cage, a common surface is conventionally provided adjacent the front panel of the plug-in unit to function as a fixed ejection surface for any ejector mounted to the front panel member.
A typical prior art ejector facilitates the removal of the plug-in unit by using a pivoting lever arm to bear against the fixed ejection surface and reduce the force necessary to be applied by the user. Existing ejectors typically consist of several components which must be assembled and attached to the card cage or, in some cases, to the printed circuit board. There are typically two ejectors on each printed circuit board plug-in unit, one adjacent each end of the front panel, to permit ejection of the unit without skewing or twisting of the board. One such ejector is disclosed in U.S. Pat. No. 4,603,375 to Miller, et al. which patent is hereby incorporated herein by reference.
Some ejector systems have been developed in which the ejector lever is also capable of injector operation. One type of system for accomplishing both injection and ejection involves use of a member which is pivotally mounted on the circuit board, and which includes a single finger that extends into a receiver such as a notch in the adjacent frame of the card cage. This type of configuration typically creates excessive fatigue problems on that single finger, since that single component is stressed in one direction upon insertion, and in the other direction upon ejection.
Another configuration for accomplishing both injection and ejection using the same pivotal device comprises a device which is pivotally mounted on a circuit board, and which has a receiver or notch located adjacent the card cage frame. The card cage frame includes a single member such as a panel edge that fits within the receiver or notch to provide the bearing surfaces. Again, fatigue problems are increased in this type of configuration, since a single member provides the bearing surfaces used for both insertion and ejection. Furthermore, operation of the injection/ejection systems described above involves an inherent problem of inserting the single finger within the receiver in the first mentioned embodiment, or inserting the notch around the single bearing surface in the second mentioned embodiment, during insertion of the plug-in unit. This requires proper alignment of the insertion/ejection handle or use of additional components to accomplish the alignment during the insertion process. In addition to these problems, the above-described injection/ejection systems could not be used in conjunction with present VXI printed circuit board plug-in unit technology, a new industry standard for the configuration of card cages, as required by present standard specifications, dictates use of an insertion bearing surface that is provided by an insertion member positioned on the frame of the card cage at a location which is separate and removed from the ejection bearing surface.
It would, therefore, be a substantial improvement in the technology to provide an injector/ejector system adapted for use with VXI (and other) printed circuit board plug-in unit technology, and which avoids the difficulties of existing systems such as excess fatigue on the injector/ejector members, and difficulties of insertion/ejection system component alignment during insertion of the plug-in unit. It would be a further improvement in the technology to provide such a system which would involve use of a minimum number of components, without compromising system structural strength and integrity. Such an invention is described and claimed herein.